void PreorderPrintLeaves( BinTree BT )
{
    if(BT==NULL)return ;
    if(BT->Left==NULL&&BT->Right==NULL)
    {
        printf(" %c",BT->Data);
        //return ;
    }
    PreorderPrintLeaves(BT->Left);
    PreorderPrintLeaves(BT->Right);
}
